I Saw A Mouse In My Garage, Is My House Infested?

Not necessarily. You may have just a single mouse in the house. The only way to really know is to have a professional inspect for signs of infestation or to purchase glue traps, and monitor the activity yourself. Many times a single mouse will enter a home for food or shelter if the door is left open. If you see more than one, you will need some other form of control for them.